Navigation of aircraft



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Nov. 9, 1937. H. c. HAYE$ NAVIGATION OF AIRCRAFT Original Filed March11, 1931 v 0 P 1 i we n w up, w

Han g 62 Hayes INVENTOR Patented Nov. 9, 1937 I UNITED STATES PATENTorri cs NAVIGATION F AIRCRAFT Harvey C. Hayes, Washington, D. C.

Original application March 11, 1931, Serial No. 521,686. Divided andthis application January 22, 1935, Serial No. 2,970

Claims. (Cl. 177-352) (Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 0. G. 757) This case is a division of mycopending abana nature that the radio operator can readily donedapplication covering Navigation of aircraft,- understand it and care forit. Serial No. 521,686, filed March 11, 1931. In the drawing Fig. 1illustrates one applica- This invention relates to the navigation ofairtion of my invention; Figs. 2 and 3 are diagrams craft and moreparticularly to certain applicashowing the movement of an airplane withre- 5 tions of acoustics which have for their purpose spect to theground; while Figs. 4, 5 and 6 show the aiding and safeguarding of thenavigation modified forms of my invention.

' of aircraft, especially as regards the making of Fig. 1 shows thesimplest application of this field landings under conditions of lowvisibility. arrangement wherein the enclosed area I, may

10 The various applications of acoustics for depthrepresent the landingfield having installed near 0 finding and range-finding on ships arefairly well its center a sound receiver 2 connected by elecknown and theuse of similar methods and appatrical leads 3 to a cooperating radiotransmitter ratus on aircraft has been repeatedly considered 4, theoutput of which is picked up by the radio during the past few years, ashas also been conreceiver 5 located on the aircraft 6. With this sideredthe application of more recent developarrangement the operator cruisesabout the field 15 ments having to do with the velocity and course andlistens to the noise of his own plane as though of ships relative to thesea-bottom which are not he were standing near the receiver on thefield. so generally known. During this time a study By noting the changeof intensity or pitch of his of the problem has led to certainconceptions incraft's sounds he can determine with considervolvingvarious combinations of radio and acous able accuracy when it passesabove the receiver. 20 tical apparatus which, judging from tests whichAnother arrangement provides the aircraft have been carried out, promiseto operate successwith a sound transmitter (not shown) capable fully onaircraft. These combinations all involve of sending out a strong soundsignal of a fairly a radio receiver and sound generator on theairdefinite pitch because-this permits the operator craft and soundreceiver and radio transmitter to judge more definitely and accuratelythe Dop- 25 on the ground. The sound generated on the pier effectproduced by the relative velocity and plane, which may be that whichnaturallyarises change in the relative velocity between the plane fromengine exhaust, propeller scream, vibrations and the sound receiver asthe plane passes across in general or that generated by a special soundt e f Judging fI'Om tests Which e b e 0 generating device such as asiren, is picked u made, the Doppler effect ofiers a better solution bythe sound receiver or receivers on the ground of the problem ofdetermining the instant when and transmitted back to the pilot by radio.This a straight line passing through a sound transcombination embodiesseveral advantages, among mmer. and receiver. One Of Which is fi in D 5them the following: It greatly lessens the .distion and the othermoving, intersects at right turbance of the numerous intense localsounds a g e t e u e Of the moving transmitter 6 35 which penetrate to aconsiderable extent any receive! 8as the case y The use Of t e knowntype of acoustical sound receiver that can D ppl r effect for this P pmay be d rbe mounted on the aircraft. These disturbing stood inconnection with Fi 2 d wherein sounds which are picked up because thesound he course of an airplane is shown as ed receiver is near theirsource make it diflicult for fr m lef o right along a straight line (R)at the listener to hear sound signals transmitt d constant velocity (V).The location of the sound from the ground directly, and practicallyimposreceiver is indicated by numeral 1 in each figure. sible for him tohear echoes of his own signals I 2 the P s course s S own as passinreflected from the ground. This arrangement through the receiver forsimplicity of descriptherefore offers the great advantage of having t n,d in 8- 3 the l course s a distance the sound receiver located away fromthe intense (h) from the receiver;'' being the p pe local aircraftnoises. This arrangement also perular distance from the receiver to thecourse line. mits the use of compound directive and tuned Now assume theplane is generating a sound of sound receivers, the weight and bulk ofwhich pitch (N). The receiver (Fig. 2) will pick up a 50 prohibit theiruse on aircraft, and as will be pitch higher than (N) by someamount, say(n) seen, the problems to be solved appear to demand which amount willactually be equal to the velocsuch receivers. This arrangement alsoreduces ity of the plane (V) divided by the wave-length the weight andbulk of apparatus required on of the generated sound of pitch (N). Thiswavethe aircraft to a minimum and makes'it of such iength (A) will equalthe velocity of sound in the 55 CAD Thus the Doppler efiect, which isthe difference between the frequency heard at the receiver and theactual frequency generated is given as a definite value equal to thevelocity of the plane (V) multiplied by the pitch (N0 of the soundtransmitted by the plane, andthis product divided by the velocity ofsound.in air. This latter value is about fixed but both factors of thenumerator are somewhat flexible and their product determines the valueof (n), the change of which is made use of in determining when the planepasses the receiver 1. It is obvious that as the plane passes thereceiver the pitch of the sound striking the receiver (1) will belowered an amount (n). In Fig. 2 the broken line (899l0) shows thenature of the pitch of the sound picked up by the receiver as the planemakes its transit if we interpret the vertical distance of this linefrom the flight line to represent the value of (n) the amount that thepitch received by the pick-up 1 differs from the pitch (N) of the signaltransmitted by the plane. It is to be noted that as the plane passesthrough the receiver the pitch picked up drops instantly from (N+n) to(IV-n) and that, conversely, the operator could tell when the planepassed the receiver by noting this change of pitch.

Fig. 3 refers to the general case where the flight line passes thereceiver 1 at 'a distance (h). Here the Doppler effect at the receiveris not due to the whole velocity (V) of the plane along its course, butto the component of this velocity along the line joining the planeandthe receiver, and as a result it is not constant. At any instant it isnumerically given by the relation:

N.V. cos 0 nand it is therefore obvious that the value of (n) whichdecreasesas (0) is made larger becomes less as (h) is increased. Fig. 2,(h) was made equal to zero and then the pitch changed abruptly from(N-l-n) to (N-n), but in the general case the change of pitch is notabrupt when the plane passes the receiver. But it can be showntheoretically that the rate of change of pitch is most rapid in allcases at the instant when (0) is degrees, or in other words, when theplane is passing through the foot of the line drawn through the receiverI perpendicular to the flight course. The change of pitch issufliciently rapid to be definitely noted even when the value of (h) islarge, i. e., when the plane is a considerable distance from thereceiver. The actual value of (n) as the plane traverses its course isgiven by the curved lines ll, [2 and I3, all of which pass through thefoot of the'perpendicular from I to the flight course. These threecurves represent in each case a different but definite value of (h) andthe slope of each curveat the origin gives the rate the value of (n) ischanging as the plane passes this point. Curve l3, which represents theleast slope, refers to a large value of (h),

curve 12, to a smaller value and curve II, to the v smallest value.

In practice the actual slope of these curves is not determined but theoperator has no difliculty in deciding whether the slope is steep orgradual by noting the abruptness of the change of pitch and a reasonableamount of practice should enable him to judge somewhat definitely thevalue of (h). Of course, the slope of these curves is dependent upon thevelocity of the plane (V) as well as upon (h), but this should not offerany serious handicap because the pilot can hold his speed fairlyconstant while reccnnoitering the landing field so that the variationsin the abruptness of pitch change as the field is crossed may beinterpreted as due to change in (h) and thus enable him to-judge whetherthe approaches are coming nearer or further from the center of thefield.

The. combination of acoustical and radio apparatus described gives thepilot the same information that he would gain if he stood on the fieldat the location of the receiver and heard his plane cruising about, andin the meantime was deprived of his binaural sense of direction. He

could judge by variation of intensity and pitch of the planes soundswhether it passed near or far away and when it passed perpendicularlyacross the line of sound transit. However, he could not tell the plane'scourse or on which side it passed, since such information must resultfrom his sense of direction. My apparatus gives this information becausethe receiver is located away from the intense local noises of his craftand the desired sound is brought to his cars by radio, which does notrespond to the local sound waves.

While such information would be of value to the pilot and indeed mightwell be vital, it is evident that he could locate the field and decideupon a definite landing program much better if he were not deprivedofhis sense-.of direction, which would tell him whether he crossed thefield to the right or left of the sound pick-up location. He alreadyknows the direction of his.

course from his compass bearing. As illustrated in Fig. 6 wherein anaircraft 6' is shown approaching a landing field I, by employing twosound receivers 20, 21) or two symmetrical groups of such receivers andtwo separate radio transmitters 4a, 4b, one associated with one group ofsound receivers and the other with the other group, each transmitteremploying a carrier wave differing in frequency from the other, and bysupplying the aircraft with two separate radio receiving systems 5a,512, one tuned to one transmitter and one to the other, with the outputfrom one receiver connected through one phone 50 of a head set and theother through the other phone 5d, a combination of sound and radioapparatus would be formed which would permit the operator to employ hisbinaural sense of direction to determine the direction of his craft withrespect to the line joining the two adjacent field receivers.

A somewhat simpler arrangement using tuned sound receivers located atdefinite known points about the field as shown by numerals l4, l5, l8and ll of Fig. 1 can serve the pilot to determine where he approachesand crosses the field. Suppose each of these sound receivers be tuned torespond to a definite but different frequency.

Since the general noise from the aircraft covers a wide range offrequencies of fairly uniform intensity, each receiver will respond toits own frequency component of the ship's noise with about the sameintensity if they are equidistant from the craft." Each receiver mayhave a separate associated transmitter, but it is preferred to make thepick-up of the several receivers the input to a single transmittereither in combination or by means of a rotating commutatorswitch,separately and in orderly succession, as is illustrated in Fig. 4.

In Fig. 4 the sound receivers Ma, I511, Ilia and "a correspond to, thesound receivers l 4, l5, l6 and ll of Fig. 1, and the output of each ofthese sound receivers passes to a common radio transmitter l8 at equallyspaced intervals of times In order that the sound receivers Mar -Ha maybe connected separately and serially to the radio transmitter I8, I haveshown diagrammatically a commutating arrangement in which a disc l9 ofinsulating material, but having a metallic portion 20. is rotated ataconstant speed by means of a suitable motor 2|. A plurality ofstationary brushes 22 are-provided, each'of these brushes beingconnected to one of the sound receivers |d.a l1a, while the metallicportion 20 of the commutator disc I9 is connected to the radiotransmitter I8. It will thus be observed that as the disc i9 rotateseach of the sound receivers sir-l 1a will be connected in turn to thetransmitter l8. By means of the radio receiver in the plane, theoperator will hear the differently pitched sounds picked up by theseveral tuned ground receivers and by judging their order of pick-up asthe field is approached and their relative intensity as the field ispassed, he can determine what part of the field he approaches andcrosses. If the pilot is to judge the relative intensity of thedifferent pitched notes by ear, it is preferred to use this commutatorarrangement whereby he hears the tones following one another in orderlysuccession. It is, however, also pos sible to determine the relativeintensities by the relative amplitude of vibration of reeds (not shown),one tuned, respectively to each field receiver and all driven by thecurrent output from the radio receiver, whereby each will respond to theintensity of that component of the current having to do with the pick-upof the field receiver of like tuning. It is to be understood that theparticular type or form of reed indicator does not form a part of myinvention since several well-known forms may be used. The publication ofthe United States Bureau of Standards entitled Design of Tuned ReedCourse Indicators for Aircraft Radiobeacon by F. W. Dunmore. ResearchPaper No. 28. reprinted from Bureau of Standards Journal of Research.November, 1928, shows and describes certain forms of such indicatorswhich might be used.

It is obvious that the disposition of receivers about the field can bevaried in many ways. for example, a line of receivers extending out fromthe field as shown in Fig. 5 can be used to direct a plane to the fieldand to inform the pilot when the field is reached by varying the tuningpitch of the successive sound receivers Mb. I52). I61) and Nb upward ordownward toward the field with a distinct break in the pitch when thefield is reached. In other words each of the receivers Mb, I51), 16b andNb is tuned to respond to a predetermined frequency of the sound geneated by the plane and the arrangement is such that the frequencies ofthe several receivers will vary progressively upward or downward towardthe field. The receiver llb which may, as shown, be

. mounted substantially at the center of thefield of the arrow of Fig.5, the operator will first hear a sound having, for instance, a lowfrequency, this sound being emitted from the receiver-transmitter Mb.Shortly thereafter he will hear the sound from the station l5b whichwill have a higher frequency than that of Mb. Continuing, he will hear asound of still higher frequency from station I617 and then as he nearsthe field I hewill again hear a sound of low frequency which willindicate to him that he is hearing the sound broadcast from thereceiver-transmitter I'Ib. It is to be understood that, as has beenexplained in reference to the system shown in Figure 1, each of thereceivers Mb, I51), lfib and Nb may be connected to an individual radiotransmitter or the output of all of the receivers may be connected tothe same transmitter. Such a line of single receivers can be followed bymeans of the intensity or pitch variation as each receiver is passed orif the receivers are mounted in pairs, as explained hereinbefore and i11trated in Fig. 6, the pilot can use his binaural sense to direct hiscraft from one receiver to the next.

It will be seen that I have provided combinations of sound and radiodevices that are capable of supplying the pilot with valuableinformation to assist him in making an approach and a safe descent on alanding field, and that he is able to get such information for thereason that the arrangements permit of locating the sound receivers awayfrom the intense local sounds of the aircraft which would otherwise bepicked up to give so strong a background of noise that other soundscould only be heard-with difiiculty, if at all.

While I have described my invention in connection with preferred formsand combinations,

it will be understood that I do not thereby intend to restrict myself tosuch illustrative means, as

I intend to include in my, invention all possible the pick-up of saidpick-up devices, and radio receiving means on said aircraftfor-receiving from said radio transmitter the sounds picked up by saidpick-up devices so that the pilot may determine the position (if hiscraft with respect to said landing field.

2. In combination, a pluralityof sound pick-up devices located atdefinite points on or about a landing field, each of said pick-updevices being tuned so as to respond to a definite and differentfrequency component of the sound generated by an aircraft, a radiotransmitter, connections between said transmitter and said pickupdevices, switch means in said cornections adapted to connect. saidpick-up devices separately and serially to said radio transmitter, andradio receiving means on said aircraft for receiving from said radiotransmitter. the sounds picked up by each of said pick-up devices sothat the pilot may determine the position of his craft as ,it approachesor recedes from said landing field.

3. In combination, a plurality of sound receivers located at definitepoints on or about a landing field, each of said receivers being tunedso as to respond to a definite and difierent frequency component of thesound generated by an aircraft, a radio transmitter, connections betweensaid transmitter and receivers, a commutating device in said connectionsadapted to connect said receivers to said radio transmitter in orderlysuccession, and radio receiving means on said aircraft tuned to saidradio transmitter so that the pilot may determine the position of hiscraft by noting the order of pick-up by the receivers as the field isapproached and the relative intensity of the difi'erently pitched notesas the field is passed.

4. In combination, a series of sound pick-up devices located along aline radiating from a landing field, the resonant frequency of saidpick-up devices being such that each device in said series responds to adefinite and different frequency component of the sound generated by anaircraft, a radio transmitter for broadcasting the pick-up of saidpick-up devices and a radio receiver on said aircraft and tuned to saidradio transmitter, the several pick-up devices being so arranged alongthe line radiating from the landing field as to enable the aircraftpilot to pick up progressively varying frequencies leading to or fromthe landing field and so direct his craft to said landing field.

5. In combination, a series of sound receivers located along a lineradiating from a point in a landing field, the resonant frequency ofsaid receivers being such that each receiver in said I series respondsto a definite and different frequency component of the sound generatedby an aircraft, and the arrangement of said receivers along said linebeing such that they vary in frequency response in uninterruptedsequence to- Ward said point in the landing field with the exception ofthe receiver nearest said point, which receiveris responsive to afrequency such as to break the-orderlysequence of frequencies, a radiotransmitter for broadcasting the sound picked up by said receivers and aradio receiver on said aircraft and tuned to said radio transmitter,whereby the' pilot is enabled to hear the sound of his craft as pickedup by said receivers as the air craft passes and so direct his craft tosaid land ing field.

' HARVEY C. HAYES.

